Level control



March 25, 1952 Filed Sept. 22, 1947 4 Sheets-Sheet l HIE .LINE

H//Z .LINE

ELI/E- G45' UZLET March 25, 1952 c. H. o. BERG 2,590,148

LEVEL CONTROL Filed sept. 22, 1947 4 sheets-sheet 2 sem 64s ourIN1/ENTR.

March 25, 1952 c. H. o. BERG 2,590,148

Y LEVEL CONTROL Filed Sept. 22, 1947 4 Sheets-Shea? 5 IN V EN TOR.

March 25, 1952/ c. H. o. BERG 2,590,148

LEVEL CONTROL Filed Sept. 22, 194'? 4 sheets-sheet '4 IN V EN TOR.

H7' ENE-V Patented Mar. 25, 1952 TENT ortica LEVEL CONTROL Clyde H. 0.Berg, Long Beach, Calif., assignor to Union Gil Company of California,Los Angeles, Calif., a corporation of California [application September22, 1947, Serial No. 775,554

(Cl. 18S-4.2)

23 Claims.

This invention relates to a mechanism for regulating and controlling thelevel of granular solids owing through a vessel, whereby the level ofsuch solids may be maintained at any desired point or the height of acolumn of said solids may be held constant within the vessel, which termincludes sealing legs, pipes, tubes, etc. This invention furtherpertains to improvements in the separation of gaseous mixtures byselective adsorption wherein such mixtures may be resolved into aplurality of fractions and in particular applies to the use ci the levelcontrol mechanism as hereinafter more fully described in conjunctionwith such a selective adsorption process.

The ,regulation oi the levels of granular or powdered solids is ofconsiderable importance in such processes as catalytic cracking,catalytic dehydrogenation, and other catalytic processes wherein solidgranular catalysts are employed in moving beds or streams and in variousother applications such as in selective adsorption processes where amoving bed of solid granular adsorbent is employed in the separation ofgases or liquids. For example, in moving bed catalysts and moving bedadsorption operations the operation pressure is sometimes controlledwithin the vessel or contamination of a product gas prevented by asealing leg at the top or bottom of a vessel through which is passed acontinuous flow of a solid catalyst or adsorbent. The pressure withinthe vessel or 'the prevention of contamination of a particular productgas is maintained by the pressure drop resulting from a small flow ofgas through such a sealing leg containing finely divided solids, thusthe vessel is effectively sealed from the remainder of the system. Thephysical characteristics of such sealing legs for a particularapplication, that is, the length and diameter, etc. is a function oi theparticle size of the granular solids, the gas iiow through the Sealingleg, and the various pressure differentials between individual points ofthe system.

The maintenance of a constant height of a column of granular solidswithin a sealing leg or other vessel is highly desirable to permit aconstant op-eration pressure for the production of a uniformly pure gas.lThis is particularly true in those instances in which a mechanism forcontrolling or metering the solids oW is employed within the vesseladjacent to or in conjunction with a sealing leg. For eiiectve use ofsuch a solids metering mechanism in conjunction with a sealing leg it isnecessary that a free space be provided within the vessel directly belowthe metering mechanism .or solids low controller and simultaneouslymaintain a constant level of solids within the sealing leg. The presentinvention is directed to a device for controlling such solid levels asis applicable to systems wherein there is a ow of a solid stream ofgranular solids, including any and all granular or powdered materialswhich may be handled as a semiuid.

The invention nds particular application in selective adsorptionprocesses wherein a gaseous mixture to be separated is flowedcountercurrently to a granular solid adsorbent, such as charcoal, silicagel, alumina, or the like, in an adsorption column. It is known thatcertain solid adsorbent-s such as for example activated charcoal orsilica gel will adsorb some gases such as water vapor, benzene vapor,butane, and the like, more readily than they will other gases such ashydrogen, nitrogen, methane, and the like, and that by heating theenriched adsorbent containing the adsorbed gases, these gases may beliberated substantially completely therefrom and the adsorbent afterbeing cooled is capable of further selective adsorption. This has led tothe development of various processes for the separation of gasesinvolving adsorption on solid adsorbents, heating the enriched adsorbentto liberate the adsorbed gases and cooling the thus regeneratedadsorbent for further use. Such adsorption processes are mosteffectively carried out by a countercurrent ow of the solid adsorbentand the gaseous mixture to be separated whereby the adsorbent flowsthrough an adsorption zone, one or more rectification zones, a strippingzone, a cooling zone, and thence back to the adsorption zone. Ingeneral, these functions are carried out in one or more columns makingit necessary to discharge the adsorbent irom the bottom of one column tobe reintroduced at the top of the same column or at the top of a secondcolumn which may contain, for example, the stripping zone. In eithercase it is necessary to effectively seal the column to prevent escape ofgases therefrom or the leakage of gases into the column at the point ofdischarge of the solid adsorbent. This seal is most effectivelyaccomplished by means of a sealing leg through which said adsorbent mustiow maintaining therein a column of the adsorbent having a constantlevel at a height sufficient to induce e, pressure drop therethrough ofa magnitude calculated to limit to the desired extent the ow of gaseseither in or out of said adsorption column. The present invention isdirected primarily to a means of controlling the level of the solidadsorbent in such sealing leg so as to maintain a continuous seal at thebottom of said adsorption column or columns, and in general to a meansfor controlling the level of any granular solids in a vessel, i. e., ameans of maintaining a constant height or depth of flowing solidmaterial.

It is a primary object of this invention to provide a mechanism which iswell adapted to controlling the level or the height of a column ofgranular solids within a vessel through which solids flow.

It is a further object of this invention to provide a mechanism forsolids level control wherein an effect of the position of the solidslevel is obtained which varies in a lineal` fashion with changes in thesolids level.

It is another object of this invention to provide a means for thecontrol of the quantity of granular solids in such vessels as sealinglegs, transfer lines, etc. employed in catalytic, adsorption, andsimilar processes, whereby the pressure of operation and the productpurity are directly affected.

It is a correlative object of the present invention to provide animproved process and apparatus for the separation of gaseous mixtures bycontinuous selective adsorption wherein the selective adsorptionapparatus is provided with the hereinafter described level controlmechanism which aids in maintaining a steady flow of granular adsorbent,effectively prevents, contamination of the product gas containing morereadily adsorbable constituents, and (zo-functions with the selectiveadsorption process as hereinafter more fully described to provideimproved operation eiciencies.

Other objects and advantages of this invention will become apparent tothose skilled in the art as the description thereof proceeds.

Briey the level control of the present invention comprises thecombination of a vertically movable means which is maintained in contactwith the flowing powdered or granular solids passing through aparticular vessel. This movable means may comprise a receptacle havingthe appearance of a funnel through which the solids may flow, or maycomprise a plate or other structure adapted to be yacted upon by thefrictional and gravitational forces established by the owing solids. Theaforementioned receptacle may be substituted for la grid structure whichmay comprise a cylindrical mesh or perforated tube or other mechanicalshape which is also adapted to be acted upon predominantly by thefrictional forces and to a lesser extent by the gravitational forcesexerted by the flowing solids. The movable means may further comprise acombination of the receptacle and the grid structure. The aforementionedmovable means maintained in contact with the flowing solids may besupported by a suspension arm which provides 'a restoring force whichonly partly counteracts the frictional and gravitational forces on themovable means and thus the movable means is deflected from itsmechanical equilibrium position. 'Ihe magnitude of this deflection is ameasure of the degree of change in the level or the height of a columnof flowing granular solids. Such defiections are utilized according tothe present invention to actuate an air or electrically operatedcontroller which in turn operates a pneumatic, electric, or magneticcontrol valve. The control valve is adapted to vary the rate of now ofgranular solids through the vessel in such a manner that the level orheight of the column of solids returns to the desired position.

The movable means is supported in contact with the owing granular solidsby a suspension arm Which may actuate a suitable controller through asystem of levers which in turn operates the aforementioned controlvalve. In another modication the suspension arm supporting the movablemeans is connected at right angles to a torsional tube `assembly so thatthe defiections of said movable means cause rotation of a part of thetorsional tube assembly thereby adjusting part of the mechanism withinthe controller to vary the flow rate of the granular solids throughadjustment of the flow control valve. It is preferable to employ thetorsional tube assembly rather than a mechanical system of levers sincethe torsional tube `assembly readily lends itself to this operation andrequires a minimum of leak proof pressure seals.

The torsional tube assembly referred to previously consists of a hollowtorsional tube which provides a restoring torque to the movable meanswhen the latter is deected downwardly under the action of a high solidslevel. An inner transmission shaft is positioned Within the torsionaltube and is rigidly affixed thereto at the .point where the torsionaltube assembly and the suspension arm, which latter supports the movablemeans previously mentioned, are joined together at right angles. Theother end of the torsional tube is rigidly fixed in position while theinner transmission shaft is free to rotate through a bearing. Thus,should the level of solids rise to a height above the desired value, thereceptacle land/or grid structure is deflected downwardly causing thesuspension arm also to deflect downwardly through a small arc againstthe restoring' torque of the torsional tube. A high degree of controllersensitivity is obtained because of grid structure giving a linearrelationship between the level of granular solids and the deection ofthe suspension arm. The transmission shaft, being rigidly attached `atone end to the suspension arm and free to rotate through a bearing atthe other, turns through the same arc as the suspension arm. Therotation of the transmission shaft may be employed, in one modification,to `actuate an air valve in an air operated controller which may in turnoperate a pneumatic control valve adapted to vary the rate of flow ofgranular solids. The air valve which comprises a part of an air operatedcontroller may be so connected so as to close under the iniiuence of adownward receptacle deflection and thereby effecting an increase in airpressure on a pneumatic solids control valve. The pneumatic controlvalve may beconnected so as to open and permit an increased solids flowunder the increased air pressure thereby causing the level of solids todrop and the receptacle to return upwardly to a more normal position.

The level control mechanism as just briefly described may be employedwith electrically operated controllers and electrically or magneticallyoperated solids flow control valves instead of those which are airoperated. The rotation of the transmission shaft previously describedmay be geared to suitably change a variable resistance or potentiometerand thus alter the quantity of electric power applied to an electricallyor magnetically operated solids control valve. The operation of thesemodifications is virtually the same as that wherein the controller andcontrol valves are air operated.

The elements of the present invention and its application to the controlof the level of a granular adsorbent in the selective adsorption processmay be more fully understood by reference to the accompanying drawingsin which:

Figure l is a vertical cross section of an elevation View of a selectiveadsorption apparatus operating in conjunction with the solids levelcontrol mechanism as hereinafter more fully described.

Figure 2 shows ya vertical cross section of an elevation View of onemodiiication of the grid structure, the receptacle, suspension arm,housings, controller and solids control valve of the level controlmechanism,

Figure 3 shows a plan View of a horizontal cross section of thesuspension arm and torsional tube assembly of the level controlmechanlsm.

Figure 4 shows a second modication ofthe grid structure, receptacle, andsuspension arm of the level control mechanism operating in conjunctionwith an electrically operated controller and solids control valve,

Figure 5 shows an elevation view of a vertical section oi' a thirdmodiiication of the grid structure supported from above in absence orthe receptacle by a suspension arm and torsional tube assembly operatingin conjunction with an air operated controller and a pneumatic solidscontrol valve,

Figure 6 shows a plan view of a horizontal section of the equipmentshown in Figure 5,

Figure 7 shows an elevation View of the level controlled mechanism inIwhich the movable means is suspended from above the level to becontrolled and indicating and controlling the rate at which the granularsolids are introduced into the vessel, and

Figure 8 shows a vertical section of an elevatio view of the levelcontrol mechanism in which the movable means is suspended from below thecolumn of solids to be controlled and also varying `the rate ofintroduction oi solids into the vessel.

For purposes of convenience in illustration and to permit a more luciddescription of the present invention the operation of the level controlmechanism of the present invention will be described in connection withthe selective adsorption process and apparatus operation in which asingle adsorption column is employed. It is to be understood, however,that the level control mechanism of the present invention which ishereinafter more fully described is not intended to be limited orconiined in its application to the selective adsorption processv inwhich a single adsorption column is employed, but that the level controlmechanism may likewise be employed without modicaton in selectiveadsorption processes in which two or more columns are employed wherein,for example, the adsorption zone may be contained within the iirstcolumn and the desorption or stripping zone contained within the second.It is also to be understood that the level control mechanism is equallyeffective in the control of the level of solids employed in otherprocesses besides that of selective adsorption such as catalyticcracking, dehydrogenation, and like processes and that the followingdescription is presented in connection with the selective adsorptionprocess in order to more clearly portray the method and advantages ofthe level control mechanism of the present invention.

The level control apparatus of the present invention is applicable togood advantage in the control of solids levels involved in the selectiveadsorption apparatus employed for the separation of normally gaseousmixtures. Briefly the selective adsorption process comprises theseparation of gaseous mixtures by contacting such mixtures withquantities of a solid granular adsorbent in a moving bed wherein themore readily adsorbable constituents of the mixture are adsorbed leavingthe less readily adsorbable constituents as a substantially unadsorbedgas. A solid bed of granular adsorbent ilows downwardly through anadsorption column to countercurrently adsorb from the gaseous mixturethe more readily adsorbable constituents thereby forming a richadsorbent. In a lower portion of the column the rich adsorbent is heatedand the adsorbed more readily adsorbable constituents are desorbed toform a rich gas.

Such an adsorption apparatus may be employed in the separation of a widevariety of gaseous mixtures on a suitable adsorbent which may includesuch adsorbents as activated charcoal, silica gel, activated bauxite,activated alumina, and the like. For purposes of description of theselective adsorption process in connection with Figure l it will beassumed that the gaseous mixture to be separated comprises methane andC2, C3 and C4 paraiins and olens which may or may not contain smallamounts oi gases of higher or lower molecular weight, and that thegranular adsorbent employed comprises activated charcoal.

4Referring more particularly to Figure l, the gaseous mixture to beseparated is introduced to adsorption zone II of adsorption column Iiiby means of line I2 controlled by valve I3 and is distributed -withinthe adsorption zone II by means of disengager Ill. Disengager I-l, aswell as the other disengagers in the column may be any desired type suchas for example a tube sheet with short tubes extending downwardlytherefrom as shown in the drawing. A solid bed or granular charcoalilows downwardly by gravity through the adsorption column at such a ratein relation to the gaseous feed rate that substantially all of the O2and heavier hydrocarbons are adsorbed by the charcoal in adsorption ZoneI I to form a rich charcoal while the methane and gases of lower normalboiling point which may be present in the feed pass `upwardly throughadsorption zone II and may be withdrawn therefrom by means of line I5controlled by valve I6. rlihe amount of lean gas withdrawn fromadsorption zone II may be controlled so as to force the passage of aportion of the lean gas through the'tubes of cooling zone 57 immediatelyabove as hereinafter described.

The rich charcoal passes from adsorption Zone il through disengager Illinto the rectication zone IQ. Here the methane and lighter gases whichmay have been adsorbed are desorbed from the rich charcoal by contactingthe rich charcoal with a side cut gas reux containing C2 hydrocarbonswhich are desorbed from the charcoal at a point lower in the column.Thus, in the rectication zone I9 any residual methane or lighter gaseswhich may have been adsorbed by the charcoal passing downwardly throughdisengager I4 are desorbed by virtue of the selective adsorptionexhibited by the charcoal for the Cz hydrocarbons which are passedupwardly through disengager 2U into the rectification zone I9. Thedesorbed methane and lighter gases then flow upwardly countercurrent tothe charcoal through disengager I4 and return to adsorption section II.

The rectified charcoal thus foimed is substantially free of such lightercomponents and passes from rectication zone I9 through disengager 28into a second rectication zone 2i In second rectication zone 2i, therectied charcoal is contacted with a rich gas reflux containing heaviercomponents in the feed, i. e., C3 and C4 hydrocarbons, to eiect thedesorption of the C2 hydrocarbons from the rectied charcoal. The levelof the C3C4 reux may be controlled at a given point within secondrectiiication zone 2l by utilization of the temperature rise within thatzone resulting from the heat of adsorption of the C3 and C4hydrocarbons. By injecting, or otherwise introducing C3 and C4hydrocarbons into the second rectication Zone 2l to serve as refluxtherein the C2 hydrocarbons are desorbed due to the preferentiallyadsorption of the heavier hydrocarbons, and the Cz hydrocarbons flowupwardly in the zone and a portion of the C2 hydrocarbons may be removedfrom second rectification zone 2! by means of line 22 controlled byvalve 23 as a side cut gas product. However, all of the C2 hydrocarbonsare not removed, a portion being passed upwardly through disengager 2ointo rectification zone lil to accomplish the double purpose ofcontacting the rich charcoal in rectification zone li] with a side cutgas reflux to effect the desorption of the methane and lighter gases asabove described, and at the same time to `insure a continued retentionof the charcoal flowing downwardly through disengager 25 of the heaviercomponents of the feed so as to prevent any desorption of these heaviercomponents in the upper portion of second rectication sone 2l inasmuchas such desorption would adversely effect the purity of the side cut gasproduct obtained. fn this manner a side cut gas is obtained comprising acomparatively pure mixture of ethane and ethylene.

The charcoal, substantially free of the C2 hydrocarbons and lightergases, passes from second rectification zone 2l through disengager 24into stripping zone 25. ln stripping zone 25 the charcoal nows throughthe externally heated tubes and is contacted therein by steam flowingupwardly within the tubes countercurrent to the downward now ofcharcoal. This steam is introduced at the lower portion or" strippingzone 25 by means of line 2S controlled by valve 2l. The tubes instripping zone 25 through which the charcoal must flow are heatedexternally by A means of flue gas, steam, organic compounds such asdiphenyl or diphenyl oxide or mixtures thereof, or the like, which maybe introduced to the zone by means of line 28 controlled by valve 2B andremoved1 therefrom by means of line 3S controlled by valve 3l. rlhesteam passes counter-currently to the heated charcoal through thestripping tubes, strips the hydrocarbons from the charcoal and the steamand the hydrocarbons are removed from the column at disengager 2li bymeans of line 3?. controlled by valve 33. At this point alternativemethods of procedure may be followed: in one, a portion of thesteam-hydrocarbon m'xture may be passed upwardly through disengager 2ito act as reilux in second rectiiication Zone El, as described above, orall of the steam-hydrocarbon mixture may be removed by means of line 32,the hydrocarbon separated from the steam and reintroduced into the lowerportion of second rectification zone 2l by means of line 3ft, controlledby valve 35. The charcoal passing through stripping zone 25 flows intothe lower portion of the column at which point the rate of flow of thecharcoal is most conveniently controlled. Any desired means ofcontrolling this flow may be employed such as charcoal feeder il shownin the drawing, or the like. This charcoal passes through feeder il intothe lower portion of the adsorption column from whence it ows into thelevel control apparatus of the present invention. The level of thecharcoal is maintained at a constant position in the bottom ofadsorption column l@ while continuously flowing downwardly through the4level control mechanism.

The charcoal owing through valve enters the gas liftJ system i8 and iscarried therein by means of gas stream furnished by blower 52 into thecharcoal gas separator 53 and flows from this separator into hopp-er Ellat the top of the adsorption column. The gas employed in the gas liftsystem is removed from hopper all by means of line 55, the major portionthereof being returned by means of line ed to the blower 52. Thecharcoal flows from hopper ne through the cooling zone 5l and throughdisengager 58 into adsorption Zone Il to complete the cycle. The leangas take-oli` valve it may be so controlled as to force a portion of theunadsorbed components of the feed to ow countercurrently to the charcoalthrough the cooliirT tubes in cooler 5l and may be removed from the topof the column by means of line 55, a portion of which may be vented bymeans of line E9 controlled by valve @il or this lean gas may be used asmakeup gas to the gas lift system in which case it is returned to blower52 by means of line 5-3. This lean gas flow through cooler El serves tosaturate the cooled lean charcoal with the constituents of the lean gasand also to remove traces of water which may be present on the charcoal.

The function of the level control mechanism, as hereinafter described ingreater detail, is to aid in maintaining a steady and regular charcoalnow across the entire cross sectional area of adsorption column le. ltalso prevents portions of the lift gas from entering the bottom of theadsorption column by maintaining a constant height of charcoal abovevalve l and effects a seal against an upward flow of lift gas.

Referring now more particularly to Figure 2, a solids level li isrequired to be maintained in the bottom of vessel lll. A continuousdownward new of granular solids passes through vessel 'IEB accumulatingin the bottom and the level control mechanism of the present inventionis employed to maintain solids level ll in appmrinately the positionshown in Figure 2. rlhe essential elements of this modification of thelevel control mechanism include movable means comprising receptacle l2and grid structure which preferably extends upwarily from receptacle l2through the bottom opening of vessel lil to a height somewhat abovesolids level i l. The movable means is positioned along the Verticalaxis of vessel l'l, supported in such a position by suspension arm lilwhere it may deflected by frictional and gravitational forcesestablished by the flowing granular solids. Other elements of the levelcontrol mechanism include receptacle housing "i5, suspension arm housing"iii, air-operated controller ll, sealing leg l, sealing gas disengagingzone lil, solids iiow control valve ii, and transfer line 3l. Thegranular solids flow downwardly from the bottom of Vessel lo as a densephase, through and around grid structure 73,

through receptacle l2 and sealing leg T3, and are discharged through thefree space between the lower end of funnel 82 and valve plate 33. Thedegree of opening or of separation between the lower end of funnel 82and valve plate 83 governs the rate of `flow of solids downwardly fromthe lower portion of vessel lil. The granular solids are removed fromseal gas disengaging zone lt by means of transfer line 8l at acontrolled il'ow rate.

Vessel 'it is provided with conical bottom sec tion lili having a bottoil opening of diameter D1. A cylindrical section Z55 having a diametergreater than that of the bottom opening is directly attached along thesame vertical axis to section 84. Cylindrical section 85 is providedwith i'lange 3% by means of which receptacle housing 'i5 is attached.The lower portion of receptacle housing 'l5 is provided with flange 8lwhich"y permits rigid attachment of sealing leg T8 bymeans of ilange E8.

Receptacle l2, which is suspended adjacent to and below the bottomopening of vessel l, consists of upper cylindrical section 89, conicalsecn tion @6, and lower cylindrical section 9! which latter is a minimuminternal diameter D2. It is desirable although not absolutely necessarythat D1 be somewhat larger than D2.

Sealing leg 'i8 is provided at the upper portion thereof with funnel 92to which is attached flange S3, flanges 8l and 83 being directly boltedtogether to form a rigid assembly. Funnel @t is further provided withreceptacle guides 93 adapted to maintain receptacle 12 in a stableposition along the vertical axis of sealing leg iii within receptaclehousing l5 while permitting receptacle i2 to move freely along thevertical Suspension arm housing c is rigidly attached by means or" ange93 to the torsional tube assembly housing, not, shown, and which willsubsequently be more fully described in connection with Figure 3.

The lower portion of sealing leg i8 is provided with seal gasdisengaging zone 'i9 as previously indicated. in order to prevent thecontamination oi gases present above soli-ds level 'il with gases whichmay flow upwardly through transfer line 3l ccuntercurrent to thedownwardly flowing solids, seal gas line 94 controlled by valve 95 isprovided to remove a seal gas from zone l. Funnel t2 is provided withindisengaging Zone 'i9 and adjacent to and below the lower end of seallegit in order to disengage gases from the granular solid in sealing leg ISso that any surges or other changes in gas flow rate Will not ad verselyail-ect the solids flow rate through the opening between valve plate 83and the bottom ot funnel 32. Gases llc-wing downwardly through sealingleg are disengaged from the solids in funnel t2 and are removed throughthe annular space between the upper end of funnel 52 and the lower endof sealing leg 18 and substantially no flow exists through the spacebetween the lower end of :funnel 82 and valve plate 83.

Solids flow control valve Si? may comprise, in the present modi-cation,a spring loaded pneumatically operated diaphragm valvemodified to theextent that valve plate 823 is direct-ly attached to valve stem Inessence, air operated controller 'Il comprises xed valve 9'! andvariable valve 953 and is provided with air inlet line Sil and airoutlet line The degree of opening of variable valve 93 is changed by avertical movement of receptacle l2. A continuous flow of air ismaintained through inlet line 99, through fixed valve 9?, throughvariable valve 93 and through outlet valve It@ and the pressure of theair entering line 99 is maintainedat a constant value. Fixed valve 9Tprovides a restriction to the ilow of air and during operation avariable pressure drop occurs across this restriction so that themagnitude of the air pressure transmitted from air operated controller'il to diaphragm chamber 10| of solids control valve @il by means ofline |82 is a function of the setting of ilxed valve 91 and of variablevalve e3. For example, if solids level li rises above the desired valuethe force acting downwardly on grid structure 'i3 and upon receptacle l2is increased and may be utilized in decreasing the opening of variablevalve 98. This action increases the pressure drop maintained acrossvariable valve S8, decreases the volume ow rate of air passing throughboth valves 91 and 93 therefore decreases the pressure drop existingacross fixed valve 9'? and as an end result increases the absolutepressure transmitted by means of line i222 to diaphragm chamber 10|.rlhe increase in pressure Works against the spring loading of controlvalve 8i) thereby causing an increased iiow rate of solids which in turncauses solids level 'il to return to more nearly a normal or desiredvalue. A valve po-sitioner as often employed with pneumatically operatedflow control valves may be employed to advantage in conjunction withsolids flow control valve 80. A pulsation dampener, not shown, may beemployed in conjunction with air operated controller 11 to eliminatesurge eiiects caused by changes in air pressure and thereby improve thesmooth solids flow and level control operation inherent in the mechanismshown in Figure 2.

The change in the downward force acting upon grid structure 'i3 issubstantially a linear function of the change of position of solidslevel TI With relation to grid structure 'i3 at a substantially constantsolids flow rate. The absolute value of the change in downward actingforce with respect to a unit change in position of solids level l! bevaried somewhat by employing different modifications in the physicalconstruction of grid structure i3. It has been found through experimentthat the change in downward acting force in pounds per inch of variationin the height of 'the solids level may be calculated from the followingequation:

@EL ce w` ere ,o is the density of the solids in pounds per cubic footand A is the cross sectional area in square inches ci the grid structurecalculated from the outside diameter oi the grid structure. rlhevalidity of this relationship has been determined with such materials assynthetic bead cracking catalyst having an average bead diarneter ofabout 6.2 inch and granular charcoal having a l2 to 20 mesh size.

Grid structure 'i3 shown in ligure 2 comprises a series of plates itshaving a diameter somewhat less than Di arranged parallel to and spacedequidistant from each other. The spacing distance may about equal to thediameter of plates ist. A series of vertical tie rods IM arranged incircle and extending upward from conical section @il ci receptaclel to aposition somewhat above solids level 'ily is employed to maintain platesi573 in their proper position and support the grid structure as a whole.The centers of plates are preferably removed leav- 13 tion shown. Thesolids flow downwardly from the bed below level il through conicalbottom section 311, through a sealing leg T8, through a seal gasdisengaging zone l, through a solids flow control valve il, and areremoved by means of transfer line 8| in a similar manner as described inconnection with Figure 2. Parts of the apparatus shown in Figure whichare similar to those shown in Figure 2 are indicated with the samenumbers. 13 is shown in Figure 5 and which comprises a tube which may beprovided with perforations or slots. The tube is arranged in a Verticalposition along a vertical axis. It is possible to position gridstructure 'i3 in substantially any vertical position within vessel 'l0as well as along the vertical axis of vessel iii. However, it isdesirable that the grid structure be centrally located so that the upperportion of grid structure 13 is above solids level 7| and that structure13 extends downwardy a substantial distance below solids level 1|. Aninternal torsional tube assembly housing E29 is shown extending acrossfrom one side of vessel 'l to the other, but displaced irom the diameteroi the vessel. Torsional tube assembly comprises the torsional tube andinner transmission shaft not shown in this ligure but extends along thesame horizontal axis within internal torsional tube assembly housing 29and in the same relationship to each otheras indicated in Figure 3. Acrank connection lll is maintained at the approximate center of thetorsional tube assembly to which the suspension arm is connected atright angles and extends outwardly therefrom in a horizontal planetoward the center of vessel lll. An end View of suspension arm is shownas |39 in Figure 5. Grid structure 'i3 comprising a slotted orperforated tube or any of the other modified grid structures previouslydescribed is suspended downwardly from the near end |30 of thesuspension arm. rlhe slots or perforations, when used, should have aminimum dimension which is suicient to permit a substantially unimpededflow of solids therethrough. As previously. described, the torisionaltube is rigidly xed in position at crank connection |86 and at each endA modication of grid structure of torsional tube assembly housing li.However, one end of the inner transmission shaft as before is free torotate through the same arc as the suspension arm, while the other endis fixed in position. The inner transmission shaft extends outwardlythrough the wall of vessel "it, through suspension arm housing lo,through controller housing ll into air operated controller Thiscontroller may just as conveniently comprise an electrically operatedcontroller similar to that described in connection with Figure 4. Therotation of the inner transmission shaft serves to change the opening ofvariable air valve 98 thereby changing the air pressure transmitted todiaphragm chamber loi by means or" line |62. Changes in air pressurethus introduced to diaphragm chamber lill change the degree of openingof solids flow control valve Si? thereby allowing level oiysolidsiiowing through the system to more nearly approach the desired value bychanging the rate of iiow of solids removed from the system by meanstransfer line iii.

Referring now noreparticularly to Figure 6 a plan view oi themodification oi solids level control mechanism shown in Figure 5 isdepicted. Grid structure 'i3 which comprises movable means in thismodiiication is shown suspended by suspension arm 'M which is rigidlyattached to the torsional tube assembly positioned within assemblyhousing |29 by crank lconnection |66. The torsional tube assemblyincludes torsional tube |61 and inner transmission shaft Hi8 asdescribed and shown in Figure 3. Inner transmission shaft extends intocontroller ll wherein it varies the opening of an air valve, not shown,which in turn actuates a pneumatic control Valve also not shown, whichis adapted to vary the rate of flow Lof granular solids passingdownwardly through vessel T0 in accordance with the position of thesolids level in vessel 10 or in accordance with the height of a solidslevel above a certain point in the system as described in conjunctionwith previous figures. Comparison of the plan view of Figure 6 and theelevation view of Figure 5 gives a clear description of this modicationof the level control mechanism.

Referring now more particularly to Figure '7, an additional modification`of the level control mechanism is shown in which the movable meansmaintained in contact with the iiowing solids is supported from abovethe level of solids to be controlled and serves to actuate a controllerwhich in turn varies the flow .rate of solids introduced into the vesselwherein the level is desired to be maintained. Granular solids flow fromhopper |35 downwardly through solids iiow control valve 19 hereinadapted to control the inlet solids flow rate. In this modification oflevel control mechanism valve stem 96 is provided with an indicator ISSand scale |31 which serves to indicate the degree of opening of solidslevel control valve |44 and correspondingly the rate of flow of granularsolids passing therethrough. The granular solids ilow downwardly throughconduit |38 and enter vessel 3S wherein a solids level |40 is desired tobe maintained at a. constant height above the bottom of the vessel.Movable means or grid structure 13 comprises in this modification avertically positioned perforated tube suspended from above by means oflever lil-I which extends into air operated controller |42. The innerworkings of controller |42 may comprise a. mechanism similar to theelectrical mechanism described in connection with electrically operatedcontroller IIB of Figure 4 or air-operated controller 'Il of Figure 2 orFigure 5. The frictional and gravitational forces exerted on movablemeans 13 are transmitted through lever |4| into controller M2 wherein avariation in air pressure is made through line |43 into the diaphragmchamber of pneumatically operated control valve |445 thus varying therate of flow of granular solids downwardly through conduit |38 intovessel |39. operated controller and control valve may be substituted forthe air-operated mechanism shown in the present ligure. If desirable atorsional tube assembly may be employed instead oi suspension arm andlever Uil. The modification of level control mechanism shown in Figure 7is one in which movable means is supported from above the level to becontrolled and the rate of granular solids entering the system ratherthan leaving the system is controlled.

Referring now more particularly to Figure 8, a modification of the levelcontrol mechanism is shown in which the movable 'means is supported frombelow and the rate of introduction of granular soli@ is controlled.Granular solids are introduced by means of line and pass through solidscontrol valve |5| for introduction at a controlled flow rate into vessel|52 establish- An electrically ing a solids level |53. Movable means inthis modification comprises grid structure 13, supported on plate |54and provided with guides |55 and |53a to assure a smooth verticaldeflection. rThe downwardly acting frictional and gravitational forcesestablished by the flowing solids is transmitted through receptacle |62maintained Within receptacle housing |63 and subsequently throughsuspension arm |51 into controller |58. The degree of deflection of themovable means actuates controller |58 so that an adjustment is madethrough line |59 in the degree of opening the solids flow control valvel5 l. Granular solids, thus controlled, flow downwardly through Vessel|52 through and around movable means which comprises grid structure 13,plate |555, and receptacle |62, and continues downwardly throughreceptacle housing |63 through line |60 controlled by restriction IBIwhich may comprise an orice thus providing a constant rate of granularsolids discharge.

The various modications of torsional tube assemblies, grid structures,electrically or air operated controllers and solids control valves maybe used interchangeably with all of the modications of the level controlmechanism herein described. For example, the modiiication of receptacleand grid structure shown in Figure l is applicable for use with thetorsional tube assembly shown in` Figure 3 or the internal torsionaltube assembly described in connection with Figure 5 wherein the gridstructure is suspended from above without the receptacle. Electricallyor air-operated controllers and solids flow control valves may be usedinterchangeably with various types of torsional tube assembly and gridstructure. Each of these modifications of level control mechanism iswell suited with the flow and level control of substantially anypowdered or granulated solid material which may be handled as asemifluid. For example, such solids as granular sugar, sand or gravel,granulated chemicals or other crystalline matter and other such massesof solid particles. The foregoing illustrations and descriptions thereofhave therefore not been intended to be limited in particularcombinations of elements shown in the particular iigure but rather toshow a series of modications of an apparatus well adapted to theaccurate control of a solid level in a conduit, vessel, transfer line,or the like. Furthermore, the description or the usage of the levelcontrol mechanism herein described with the selective adsorption processis likewise not intended to serve as o-r denne any limitations to theusage of the level control mechanism for the operations and function ofthe level control mechanism is independent of the particular nature ofthe process in which granulated solids are employed or thecharacteristics of the particular granulated solids used.

Many modifications in the operation and in the design of the adsorptionunit may be employed without departing from the present invention whichcomprises the usage of a new and improved type level control inconjunction with the selective adsorption process. For example, it maybe desirable to divide the operation, separating the processes ofadsorption and stripping into two separate columns wherein, as in theabove described example, the heart cut would be obtained in the initialcolumn by introducing the heavier components obtained in the strippingcolumn as reux to eiect the desorption of the intermediate components.In another modification an elevator type charcoal conveyance may beemployed in place of the gas lift system as described. In such case thecharcoal ilowing through the control valve 45 would be deposited in abucket conveyer and carried directly to the top of the column of if atwo-column operation were employed the enriched charcoal flowing fromthe lower portion of the adsorption column would be transferred by anelevator to the top of the stripping column and the charcoal flowingfrom the lower portion of the stripping column would be conveyed bymeans of an elevator to the top of the adsorption column. It should beemphasized that if a two-column operation is employed it is highlydesirable to employ a level control as herein described at the bottom ofeach of the columns so as to maintain a constant level therein.

Wherein the adsorption process is described with reference to a modifiedprocedure wherein the heart cut is obtained from the gaseous feed it isto be understood that the present invention, pertaining to an improvedmethod and apparatus for the control of the level of granular solids andfor the usage of such apparatus in conjunction with the adsorptionprocess, is equally effective when this process involves solely theadsorption of certain components from a gaseous mixture followed only bythe subsequent recovery of the adsorbed components from the adsorbent bysteam stripping or the like. Whereas, I do not intend to be limited tocharcoal adsorption, charcoal is the preferred adsorbent particularly tothe separation of hydrocarbon gases. The charcoal employed in the aboveprocess is preferably granular, about l0 to 20 mesh, although sizes asmuch as about 4 mesh and as small as about mesh may also be employed.The term charcoal used herein is meant to include any animal, vegetable,or mineral charcoal, or the like, although an activated form ofvegetable carbon or charcoal prepared from coconut hulls or fruit pitsis preferred. After long usage small amounts of highly adsorbablematerial may accumulate on the charcoal and hamper its eiciency in whichcase the charcoal may be withdrawn from the column and may bereactivated by a high temperature steam treatment.

Whereas, particular emphasis has been placed upon the usage of theimproved level control in conjunction with the charcoal adsorptionprocess, it should be apparent to those skilled in the art that thislevel control will iind application in any process or in any usage inwhich granular solids are passed from a vessel and at the same time areemployed to prevent ingress or egress of gases to or from this vessel.Such a situation may occur, for example, not only in selectiveadsorption process as described, but in many catalytic processes such ascracking, dehydrogenation, and the like, as well as in various treatingprocesses, etc. It is therefore, within the scope of this invention toemploy a level control as described in any operation in which thefunction thereof is of importance or is required.

Having described and illustrated my invention with respect to theprincipal elements thereof and its usage in conjunction with adsorptionof other processes in which granular solids are employed 'and realizingthat many modications thereof will occur to those skilled in the artwithout departing from the spirit or scope of the foregoing descriptionand the following claims.

I claim:

l. An apparatus for maintaining a column of flowing granular solids at aconstant height 17 which comprises movable vertical. grid meansmaintained in contact with said owing; solids and a solids iiow controlvvalve, said; movable grid means being cylindricalin shape andzhavingperforations sufcient to permit. a substantially unimpeded iiow ofsolids therethrough,` and thereby permit said movable grid means to. beacted upon by the frictional. and gravitational forces established bysaid' owing granular-solids so as to cause a deiiection of said. movablegrid means in accordance with the varying: height of said solids, andsaid solids control valve adapted to vary the rate of'ow of' saidgranular solids in accordance with said deflection.

2. An apparatus for maintaining. a'. colu'mrr of flowing granular solidsat a. constant lheight which comprises in combination afinowableAvertical grid means in contact with said; solids', acontroller, and asolids now control valve, said movable grid means being cylindrical inshape. and having perforations suicient to permit a substantiallyunimpeded ilow of solids therethrough and thereby permit said'- movablegrid' means to be deflected by frictional and gravitational forcesrestablished by said flowing solids in accordance with the heightthereof, said controller adapted to be actuated by said. deilection ofsaid movable grid means and said controller being also adapted toactuate said solids flow control valve to vary the rate of il'ow ofsaidv granular solids.

3. An apparatus for controlling the level of granular solids. atta xedpoint above a discharge control valve which comprises in combination avertically movable vertical grid structure disposed adjacent to thelevel to be controlled, said movable grid being cylindrical in shape andhaving periorations sufficient to permit a substantially unimpeded flowof solids therethrough, a suspension arm supporting said grid structure,a torsional tube assembly` attached tosaid suspension arm, and acontroller adapted to adjust said control valve and thus vary the flowrate of said granular solids in accordance with the level of saidsolids.

4, An apparatus according to claim 3 wherein said grid structure extendsthrough the level of solids to be controlled.

5. An apparatus according to claim 3 wherein said grid structure issupported by said suspension arm from above the level of solids to becontrolled. i

6. An apparatus vaccording to claim 3 wherein said grid structure issupported through said suspension arm from below thelevel oi solids tobe controlled.

7. An apparatus according to claim 3 wherein said controller and saidcontrol valve `are air operated. 8. An apparatus according to claim 3wherein said controller and said vcontrol valve are electricallyoperated.

9. An apparatus for controlling a level of granular solids in vesselswhich comprises in combination a vessel provided with means for theintroduction of granular solids substantially above the bottom thereof,a bottom opening through which said granular solids are discharged, avertically elongated and vertically movable grid structure extendingupwardly through the bottom opening of said vessel and extending throughsaid level of solids to be controlled, said grid structure resting on avertically movable receptacle which has a minimum diameter less than thediameter of the bottom opening of the vessel, and is supported belowsaid solids level to be controlled, a suspension arm supporting; saidreceptacle, a torsional tube assembly attached at right angles to saidsuspension arm, an air-operated controller and an air-operated controlvalve adapted to vary the rate at which said solids are dischargedthrough said bottom opening of said vessel in accordance with thelevelof said solids.

10:. An apparatus according to claim 9 wherein said solids arecontinuously introduced into Said inlet of said vessel and arecontinuously discharged through said bottom opening of said vessel, saidsolids continuously owing downi wardly through and around said gridstructure and continuously downwardly through said re"-- ceptacle. p

1l.. An` apparatus for circulating a moving bed of granular solidsthrough a column containing gas under pressure without permittingexcessive flow of gas with the solids removed from said column, whichcomprises an elongated sealing leg below said column and communicatingtherewith, a solids control valve at the bottom of said sealing leg,means for recirculating solids withdrawn from said column through saidcontrol valve to the top of said column, a solids feeder near the lowerend of said column adapted to support a continuous bed of said solidsthereabove and discharge them into a free space in the lower portion ofsaid column, and means for automatically maintaining a moving bed ofsolids in said sealing leg with a solids level in said free space, saidlast named means comprising the combination oi a vertically elongatedand vertically movable grid structure extending through said solidslevel in said free space, a suspension arm supporting s aid gridstructure, a torsional tube assembly rigidly attached at right angles tosaid suspension arm, a controller attached to said torsional tubeassembly, said controller being adapted to operate said control valvewhen actuated by said torsional tube assembly so as to vary the flowrate of granular solids through said sealing leg in accordance withsaidsolids level.

l2. An apparatus according to claim 1l wherein said grid structure issupported from above said solids level by said suspension arm, andwherein said suspension arm and said torsional tube assembly arepositioned within said free space in said column.

18. An apparatus according to claim l1 wherein said vertically movablegrid structure is supported by a suspension arm positioned below saidsolids level wherein said solids flow downwardly through and around saidvgrid structure.

14. An apparatus according to claim 11 in which said torsional tubeassembly comprises a hollow torsional tube rigidly attached to saidsuspension arm at one end and rigidly attached to said column at theother, and an inner transmission shaft rigidly attached to saidsuspension arm at one end and. free to rotate at the other.

l5. An apparatus according to claim 11 wherein said grid structure issupported on a receptacle adapted to receive solids discharged from thebottom oi said column and in turn discharge said solids into the top cisaid sealing leg, said receptacle comprising an upper conical sectionand a lower cylindrical section thereby having the appearance of afunnel.

16. An apparatus -for the separation of `a gaseous by continuousselective adsorption on a solid granular adsorbent comprising anadsorption column provided with an adsorption zone in the upper portionthereof, a stripping `zone in the lower portion thereof, means forintroducing said gaseous mixture into the lower portion ofV saidadsorption zone, means for removing the unadsorbed constituents of saidgaseous mixture from the upper portion of said adsorption zone, meansfor introducing stripping gas into the lower portion of said strippingzone, means for removing stripping gas and adsorbed constituents of saidgaseous mixture from the upper portion of said stripping zone, anelongated sealing leg below said column `and communicating therewith, asolids control Valve for controlling the withdrawal of said granularadsorbent frcm the bottom of said sealing leg, means for conveying saidgranular adsorbent withdrawn from the bottom of said sealing leg to thetop of said adsorption column, a solids feeder near the lower end ofsaid adsorption column below said stripping zone, said solids feederbeing adapted to support a continuous bed of said solids throughout saidadsorption zone and stripping zone thereabove and to discharge solids ata controlled rate into a free space in the bottom of said column, andmeans for automatically maintaining a moving bed of solids in saidsealing leg and controlling the level of said granular adsorbent in thefree space in the bottom of said adsorption column, said lastnamed meanscomprising in combination a 'vertically elongated and vertically movablegrid structure through and around which said granular adsorbent passes,a suspension arm supporting said grid structure, a torsional tubeassembly adapted to provide a restoring torque to said grid structurethrough said suspension arm, and a controller adapted to be actuated bysaid torsional tube assembly and adapted to actuate said control valvein accordance therewith.

17. An apparatus according to claim 16 wherein said torsional tubeassembly comprises a hollow torsional tube, and an inner transmissionshaft, said hollow torsional tube being rigidly xed at at least one endto prevent rotation thereof, said hollow torsional tube being alsorigidly attached to said suspension arm, said inner transmission shaftbeing rigidly attached to said suspension arm and free to rotate throughthe same arc as said suspension arm as said grid structure is deflectedalong a vertical axis in accordance with the height of said solidslevel.-

18. An apparatus for maintaining a constant solids level in a vesselthrough which said solids are continuously owing downward in a solidmoving bed, which comprises a vertically elongated grid extendingthrough said solids level, supporting means for said grid, saidsupporting means being adapted to permit said grid to move verticallywith a variation in the height of the solids level, and means fortransmitting the motion of the grid to the outside of the vessel, saidlast named means comprising a hollow torsional tube rigidly attached tosaid vessel at one point and rigidly attached at right angles to saidsupporting means at a remote point within said vessel, and an innertransmission shaft also rigidly attached to said supporting means atsaid remote point and extending through the walls of said vessel andfree to rotate at a point outside said walls.

19. An apparatus according to claim 18 in which the grid is a verticalcylindrical screen permitting substantially unimpaired flow of solidstherethrough,

20. An apparatus according to claim 18 'in which the grid is a verticalperforated tube permitting substantially unimpaired flow of solidstherethrough.

21. An apparatus according to claim 18 in which the grid comprises aseries lof horizontal plates connected by tie rods.

22. An apparatus according to claim 11 in which the torsional tubeassembly comprises a hollow torsional tube rigidly attached to the Wallsof said column in the free space thereof and rigidly attached to saidsuspension arm at a mid-point thereof, and an inner transmission shaftrigidly attached to said suspension arm at said mid-point and free torotate at one end thereof, and the controller is an air-operatedcontroller which is actuated by the motion of the free end of saidtransmission shaft.

23. An apparatus according to claim 11 in which means are provided forintroducing a sealing gas into the free space at the top of said sealingleg, and a seal gas disengager is provided at the bottom of said sealingleg, said seal gas disengager comprising a funnel open at both ends andadapted to receive solids and sealing gas flowing from said sealing legand discharge sealing gas upward through the top of the funnel anddischarge solids downward into said control valve, a housing surroundingthe lower portion of said sealing leg, said funnel, and said controlvalve, means for withdrawing sealing gas from the upper portion of saidhousing, and means for withdrawing solids from the lower portion of saidhousing.

CLYDE H. O. BERG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 234,747 Boynton Nov. 23, 1880510,954 Beall Dec. 19, 1893 1,115,193 Hay Oct. 27, 1914 2,304,827 SewellDec. 15, 1942 2,360,787 Murphee Oct. 17, 1944 2,368,672 McNamara Feb. 6,1945 2,897,566 Schutte Apr. 2, 1946 FOREIGN PATENTS Number Country Date618,502 Germany Sept. 10, 1935

